docs: def all_tokens(self, delimiter=' ', label_list_ids=None):
          """
          Return a list of all tokens occurring in
          one of the labels in the label-lists.
  
          Args:
              delimiter (str): The delimiter used to split labels into tokens
                               (see :meth:`audiomate.annotations.Label.tokenized`).
              label_list_ids (list): If not None, only labels from label-lists with
                                     an idx contained in this list are considered.
  
          Returns:
               :class:`set`: A set of distinct tokens.
          """
          tokens = set()
  
          for label_list in self.label_lists.values():
              if label_list_ids is None or label_list.idx in label_list_ids:
                  tokens = tokens.union(label_list.all_tokens(delimiter=delimiter))
  
          return tokens